Camco Propane Double-Stage Auto-Changeover Regulator- For RVs with Dual Propane Tank Hookups, Maintains a Constant Gas Pressure With Auto Change From Empty to Full Tanks (59005) Allows removal of empty cylinder for refill without interrupting propane supply Inlets are 1/4" SAE inverted flare and outlet is 3/8" NPT female pipe thread For RVs with dual propane tanks. Automatically switches from primary to reserve tank when primary is empty Primary cylinder 210,000 BTU/hr capacity; Reserve cylinder 130,000 BTU/hr Double stage design maintains constant gas pressure under changing demand and conditions